Cavendish bananas ʻGrand Nainʼ are commercially important cultivars. It belongs to the Cavendish subgroup of the AAA banana cultivar group. These cultivars face the problem of quick rotting due to infection with different phytopathogens. Gene transformation technique was used to improve the cultivar productivity and resistance to infection. Thionin genes (AT1G12660 and AT1G12663) were isolated from Arabidopsis thaliana. Thionin genes (thio-60 and thio-63) are antimicrobial genes producing antimicrobial proteins which inhibit fungal infection. These two thionin genes were integrated into the pEGAD vector. Then transformed into the tested banana cultivar via chitosan nanoparticles using the shoot tip culture technique. The chitosan nanoparticles are efficient, rapid and safe transformation technique. The resulted transgenic banana lines were partially resistant to infection by two different fungal species: Fusarium solani and Fusarium equiseti. These fungi cause rotting for the non-transgenic lines compared to the transgenic lines which resist the rotting infection due to the expressed inhibitory thionin protein. Transformation of thionin into the transgenic plants were confirmed by conventional PCR.